00:01
So this is the question that we have given.
00:03
It is given that jerry's tax messaging phone plan, she paid dollars 1 .2 for every 30 messages she sent.
00:13
So rask to find what is her cost per message.
00:18
They have given $1 .2 for 30 messages.
00:26
And then they're asking for one message, what is the rate? so let us find suppose let us consider the rate as x.
00:42
We can do cross multiplication, that is 1 .2 into 1 should be equal to 30 into x.
00:50
So x equal to 1 .2 by 30, $30 per message.
01:04
So this is dollar per message.
01:07
If you convert it into decimals, it will become $0 .0 .0 .0.
01:15
So, 0 .04 dollars per message.
01:23
So this is the answer for the first part.
01:27
And now in second part, we are asked to find which graph best approximates jury's text messaging plan.
01:34
In y -axis, they have given dollars and x -axis they have given messages.
01:39
So here, the dependent variable is messages.
01:42
Sorry the dollars since y axis is dependent so this is dependent and messages is independent is independent variable id and this is dependent so we can since this is a straight line we can write it we can write the equation as so i am doing part two here we can write the equation of a line as y equal to mx plus c so this is the general equation of a straight lane now in this equation we have to find the value of c and value of m we have one point such that when we have to send zero messages the cost has to be zero because for zero message the cost has to be zero so this is one of the point zero comma zero so if we substitute this point in the equation zero equal to zero plus c therefore we get c equal to zero therefore the resultant equation becomes y equal to so this is the resultant equation.
02:54
And now we have to find the m.
02:57
So m is nothing but slope.
03:01
As you know that slope is d -y by d -x.
03:06
Since y -axis is nothing but dollars and x -axis is nothing but messages, so the slope, the units of slope should be dollars per message.
03:16
It is nothing but what we have find here.
03:19
This is nothing but the slope.
03:21
So suppose consider this line.
03:24
If this is theta, this is equal to slope.
03:30
Similarly, this is equal to slope for this line.
03:33
This is equal to slope and this is equal to slope.
03:37
Here the slope is 0 because it is a horizontal line.
03:42
Now y equal to mx represents the line should pass through origin.
03:47
So here the lines which are passing through origin are 1, 2 and 3.
03:53
Only these 3 are passing through origin...